Hydraulic circuit



G. A. WAHLMARK HYDRAULIC CIRCUIT Sei. l', 1946.

Filed April 9, '193e 4 sheets-sheet 1 Sept. 10, 1940. G. A. WAHLMAK 2,214,389

' HYDRAULIC CIRCUIT Filed April 9, 1956 4 SheetsfSheet 2 155 T1911 m m E11 198 13g Tar/INK E20 2161?@ 2 13M 131 133136 q i'g r\ 1 30 FRSTFEED Wm 1547?@ 16g N e L10 1 0g] 1 5 1 183 166 161 217 13 139 63 37 l '175173 .S 155 210 13 v lgg 188 .154 16015 I 1 L, |51 171 r' 153 f 157 163x157 1.59 j100- 101' 60 AL/3'5 gl g l Y 165 l5@ l 100K 59 75l/116m Gunnar' J7. Zlfahzmofc,

Sept 1Q, l940- G. A. WAHI- MARK l y 2,214,389

` I I HYDRAULIC CIRCUIT Filed April 9, 19:56 l 4 sheets-sheet s v ro TANK 2112 E17 [111@ 13g 14g 13@ sept. 1o, 1940.4

G. A. WAHLMARK HYDRAULIC CIRCUIT 4 sneet-sheet 4 Filed April 9, 1 956 Patented Sept. 10, 1940 ,UNITED STATES PATENT oFFlcE 34 Claims.

The invention relates to a hydraulic circuit and has as a general object to provide a circuit having novel and improved means for supplying operating fluid to a hydraulic motor at selectively different rates for actuating a member at different speeds and underdifferent loads.

A more particular object of the invention is to provide a hydraulic circuit having novel and improved means for supplying operating uid to a reversible motor at relativelyydifferent rates' and directions of flow for reciprocating a tool or work support of a machine tool at different speeds and under diiferent loads.

Another object of the invention is to provide a hydraulic circuit, including a reversible hydraulic motor for actuating a tool or work support of a machine tool in either a forward or return direction, having novel and improved means for supplying operating fluid to the hydraulic motor in unmetered quantities and at a high rate to impart a shockless and high speed traverse" movement to the support and for supplying operating fluid in accurately metered quantities and at a low rate to impart a smooth, slow or feed movement to the support.

Another object is to perfect a hydrauliccircuit,

including a hydraulic motor, having a continu-"- ously driven variable output pump capable of metering the quantity of fluid supplied tothe motorn or capable of permitting unmetered flow therethrough so that all fluid supplied to the motor may pass lthrough the pump, andl means including a source of uid under pressure controllable to cause the pump to meter the fluid supplied to the motor, to permit unmetered ow to the motor or to permit no fluid to be supplied to the motor.

Yet another object is ,to provide a hydraulic circuit having a reversible hydraulic motor connected to a tool'or work support to be driven, a large output pump supplying fluid to the motor at a high rate to impart a traverse movement to the support, a smaller output pump supplying fluid to the motor at a lower accurately metered rate to impart a feed movement to the support,

' and novel control means for and arrangement of circuit having a reversible hydraulic motor conv nected to a tool or work support to be driven, a

large output pump supplying fluid to the motor at a high rate to impart a traverse movement to the support, a smaller positive, displacement piston pump supplying iiuid at la lower accurately metered rate to impart a-feedj movement to the 5 support, the pumps being connected in series and driven continuously so that all uid supplied to the motor passes through the piston pump, a

reversing valve directing the uid supplied to the motor to obtain movement of the support in a forward and return direction, a valve controlling the dischargeof uid from the motor to prevent Y the support from overrunning the fluid supply, a doublebypass valve controlling vthel pressure of the iluid supplied by the large output pump having three adjustments rendering either the 'large output pump'or the piston pump effective or both ineffective to supply fluid to the motor to obtain respectively rapid traverse, feed or no movement of the support, and a pilot valve for coordinating the adjustments and positions of the bypass and reversing valves to obtain a predetermined cycle of movement of the support.

A further object is to provide a hydraulic circuit of the character described in which the large output pump and the piston pump are housed in a single` casing and driven by a common shaft and in which the reversing, discharge control, bypass and pilot valves `are all housed in a single casing thereby reducing to a minimumpiping and couv plings connecting the valves, pumps and motor.

Yet a further object is to provide in a hydraulic' u circuit including a pilot valve having stop, rapid approach," feed and rapid return" positions, a remote control valve actuable to'shift the 35 pilot valve from stop to rapid approach and from feed to rapid return.

Still a further object is to provide a hydraulic circuit having a hydraulic motor for actuating a tool or work support of a machine tool, 'pump 40 means for supplying operating fluid to the motor, and a valve controlling the discharge of fluid from the motor so constructed and connected in circuit that during propulsion of the support by the tool, as in a climb cut, the pump means serves the dual function of metering the quantity of duid supplied to the motor to determine the rate and of controlling the valve so ythat it permits escape of uid from the motor only at the rate at which fluid is supplied independently of the pressure -which may build up on the discharge side of the motor. s

Still a further object is to provide a hydraulic circuit having a hydraulic motor for actuating a work support, a first pump for supplying fluid to -.the motor to drive-the support at a rapid traverse \,rate, va second pump for supplying fluid to the (linotor to drive the support at a feed rate, the feed pumpbeing manually adjustable to obtain a variety of feed rates and automatically adjustable to obtain either one of two preset rates without any by-passing of fluid, and control means for determining the rate at which the feed pump operates.

` @ther objects and advantages will become apv parent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a front elevational view of a unit, sliding, drill head reciprocated by a hydraulic motor supplied with operating uid by a hydraulic system embodying the features of the invention.

Fig. 2 is an irregular horizontal sectional Viewc showing the gearing in the drill head of Fig. 1.

Fig. 3 is a transverse sectional view taken approximately along line 3--3 of Fig. 2.

Fig. 4 is a diagrammatic view of the hydraulic circuit with .the elements shown in stop position. Fig. 5 is a diagrammatic view of the hydraulic circuit With the elements shown in rapid approach position.

Fig. 6 is a diagrammatic view of the hydraulic circuit with the elements shown in fast feed po` sition.

Fig. 7 isu a diagrammatic view of the hydraulic circuit with the elements shown in rapid return position. v

v Fig. 8 is a view of the pilot valve 'of the hydraulic circuit shown in a position which it assumes for slow feed.

Fig. 9 is a side elevational view of the casing housing the reversing valve, discharge control valve, double bypass valve :and the pilot valve of the hydraulic circuit.

Fig. 10 is a development of the valve casing showing the valves in axial section.

Fig.I 11 is a detail View of a remote control valve of the hydraulic circuit.

Fig. 12 is an enlarged fragmentary section taken through the restricted passage of the discharge control valve.

While the invention is susceptible of various modifications and alternative constructions and while it may be embodied in a variety of structures, it is here shown and will hereinafter be described in 'a preferred construction in `an eX- emplary embodiment, but it is not intended that the invention is l)to be limited thereby to the specific. construction shown but it is intended to cover all modifications and alternative constructions falling within the spirit andyscope of the invention as defined bythe appended claims.

While a hydraulic circuit embodying the featuresof 1the invention might be employed in a' variety of devices and through a hydraulic mo- 60 tor actuate a member at diiferent speeds and throughl different cycles, the hydraulic circuit is, for purposes of disclosure, herein shown and will hereinafter be described as embodied'in and actuating a unitary drill head I 2. The drill head I2 is slidable longitudinally on ways'l3 formed on the bed I4 of a machine tool and at one end carries a tooll I5, a single drill being here shown, driven through suitable reduction gearing by an electric motor I6 mounted at the other end' of the head. The reduction gearing (see Figs. 2

, be maintained with a high degree of smoothness and uniformity as compared with rapid approach and is commonly known as feed. The head is returned to normal position at a high speed comparable to rapid approach and' is termed traverse orv rapid return. The head may also be arrested tempogear 26 also fast on thesstub shaft, and gear 21 rigid with a' sleeve 28 ,.ceived partially over a rarily at some point other than its normal stop l position which is known as dwell. Movements of the head at these speeds may be arranged in any predetermined sequence to obtain the cycle of operation desired. Herein the -head I2 has a cycle of operation comprising rapid approach, fast feed, slow feed, rapid return and stop. y 'f Y To impart such a cycle of operation to the drill head I2, the hydraulic circuit herein comprises generally (Fig. 4) a reversible hydraulic tor is a reversing valve 38 directing the iiuid supplied to the motor to obtain reversal thereof. In order to avoid uncontrolled movement of the head when fthe reaction of the tool on the Work is such that it tends to advance the head, i. e., creates a negative work resistance, means generally designated 39 is provided for controlling the' discharge of fluid from the motor and this means is made responsive only to the pressure of the fluid supplied to the motor and in that manner so controls the discharge of fluid as to `prevent overrunning of the head. AControl means is also pro- -vided for governingl the rate at which fluid is supplied to\the motor to obtain the various speeds of the\head\and has a first adjustment -at which no iiuidfis supplied to the motor so thatfthe head is at rest, a second adjustment at which uid is supplied to the motor at a low accurately metered rate to obtain a feed of the head, and a third adjustment atwhich a large unmetered quantity of uid is supplied .-to the motor at a high rate to obtain a rapid traverse of the head. Herein such control means comprises simply a. double bypass valve 40 and obtains the different rates simply by control of the discharge pressure of the large output pump. The 'bypass valve 40 and the reversing valve 38 are controlled and co'- ordinated by a pilot valve 4 I to obtain the desired cycle of operation of,l the head I2. As here shown, the cycle of operation of the drill head I2 is initiated either by manual actuation of the pilot valve 4I or by actuation thereof through a remote control valve 42, the remainder of the cycle being controlled automatically through dogs (see Figs. 1 to 3) adjustably secured on a bar 43 extending longitudinally of the bed I4.

To reduce piping and couplings, .the reversing valve 38, the discharge valve 39, the bypassyvalve 48 and the pilot valve 4I are all housed in a single casing 45 which is inserted through an aperture in the front panel 44 of the drill head and secured thereto by bolts 46 extending through a ange 41, formed at one end of thecasing 45, and threaded into the drill head. The pump 36 and the pump 31 while indicated as separate units in the diagrammatic-Views, Figs4 to 7,

are in reality also housed in a single casing 48 and are driven by a common shaft 49 as more particularly described and claimed in my copending application Serial No. 141,327, filed May 7, 1937. The casing 48 is mounted on the inside of the panel 44 .and the pumps are continuously driven by the motor I6 through gear 50 fast on the common shaft 49 and idler gear ,5I meshing 'with gear 58 and pinion 29 on motor Shaft I6',

The hydraulic motor 35 comprises a cylinder 55 and apiston 56 reciprocabletherein. To facilitate the supply of operating fluid to the motor, the cylinder 55 herein is made rigid with and extends longitudinally of the drill head I2 while through a commpn supply conduit 6I.

Interposed between the supply conduit 6| and the motor 35 is the reversing valve 38 formed by a cylindrical bore 62 in the valve casing 45 closed at its ends by caps 62 and 62'?V (see Fig. 10) and in which is reciprocable a valve core 63. To direct the supply cf fluid to the motor35 in a manner to effect reciprocation thereof, the valve casing (Fig. 5) has opening into the bore 62 ve annular, -equally spaced ports 64, 65, 66, 61 and 468. Connected to the intermediate one 66 of these portsis the conduit 6|and leading from the port 65 to one end of the cylinder 55 is a conduit 18 and leading from the port 61 to the other end of the cylinder 55 is a conduit 1I. 64 and 68 are connected by branch conduits 12 and 13 to a common discharge conduit 14 which eventually leads to the;tank or reservoir 58.

The valve core 63 is provided'with three annular grooves 15 of substantially equal length and a'fourth annular groove v15', of equal length but slightly shallower than grooves 15, forming a land 16 and a land 11 at rthe extreme ends' of the core, and three intermediate lands 18. Each groove is of a length such that it is capable of embracing two ports. rThe core 63 has two positions and when shifted to the right or advance position` (see Figs. 5 `and 6) the supply port 66 and the port 61 are connected to supply operating fluid through the conduit 1I to impart movement to the head I2 in a direction lto advance the same toward the Work. In that position of the valve, ports 64 and 65 are connected to permit discharge'of fluid from the other end of the cylinder through the conduit 10. When the valve core is shifted to the left or return position (see Figs. 4 and 7) supply port 66 is connected with port 65 and port 61 is connected with valve 38.

The ports' port 68 to effec@ movement of the head in a direction away `from the work.

Movement of'the head I2 toward or away from the work at a high speed requires no high degree of uniformity and the fluid for effecting such movement may be supplied by any pump capable of a large output at the required pressure. Herein the rapid traverse pump 36 is shown as a constant displacement variable pressure pump of the rotarytypesuch as 'more particularly dis- -closed and claimed in my 'copending application Serial No. 675,218, filed June 10, 1933, issued Oct. 11, 1938 as Patent No. 2,132,813, and Serial No. 14,017, filed April 1, 1935, issued Feb. 7, 1939, as Patent No. 2,146,037. The pump 36 is continuously rotated by motor I6 and operates in well known manner to draw fluid, preferably oil,

through an rintake conduit 59 and to discharge the same to the hydraulic motor 35 through a passage formed in part by aconduit and the conduit 6I. With the entire output of the pump 36'supplied tothe motor, the head. I2 is rapid traversed in either a forward or return direction depending upon the position of the reversing When the tool is in engagement with the work, however, a slow, uniform movement of the head I2 is required and necessitates the supply to the motor 35 of a small quantity of fluid at an accurately metered rate. The means for supplying such a small accurately metered quantity of uid is the pump 31 which herein takes the form of a variable displacement pump of novel construction more particularly described and claimed in my-copending application Serial No. 141,327,

f from vthe tank or reservoir 58 icarried in the head, u

filed May 7, 1937. This pump comprises one or y more cylinders 80 having apiston 8l reciprocable therein and in all positions having one end projecting from the cylinder. The piston is actuated by a wobble plate 82 swiveled on a ball 83 and having an arm 84 projecting into a socket 85 Vformed in the end ofthe shaft 49 oblique to the axis thereof. The piston 8I merely abuts the wobble plate 82 and is not positively connected thereto so thatthe wobble plate is capable of imparting an exhauststroke to the piston but is unable to impart a return or intake stroke thereto, thus making the pump non-self-prlming.

The displacement of the pump 31 may be varied by changing the stroke of the piston 8| and this is accomplished by relative :axial adjustment of the Iwobble plate 82 and the shaft 49. Such relative, adjustment varies the/ extent to which the arm 84 is received in the oblique socket 85 therebyvarying the throw of the wobble plate. Herein this is accomplished by movement of the wobble plate` 82 and to that end the-ball 83 upon which the plate is swivelled is Aformed on the end of a piston 81 slidable in a cylinder 88. 'I'he position of the piston 81 maybe manually set at a predetermined displacement of the pump by means of rings 90 and 9Ithreaded onto the cylinder 88. To that end there is secured diametrically of the piston 81 a rod 92 projecting through longitudinal slots 93 in the cylinder 88 and between the rings 90 and 9|. Byrotation, these rings may be adjusted longitudinally uof the cylinder 88 and thus secure the piston 81 in a position resulting in a predetermined displacement of the pump. ^Theq rings 90 and 9| have worm teeth formed on their periphery 'and may be rotated by worms having kiobs 94 and y85 (Fig. 1) disposed outwardly of the drill head for-convenient adjustment of the displacement f piston 81.

4der 88 shifts the piston to reduce the displace 92 so as to permit movement of the piston under hydraulic pressure, the rings merely constituting stops limiting the extent of movement ofthe Fluid pressure supplied to the cylinment of the pump to the extent permitted by ring 90 while reaction of the piston 8| returns the piston 81 to normal position, determined by ring 9|, when no iluid is supplied to cylinder 88. The manner in which the supply of fluid to the cylinder 88 is controlled will be described here- The variable displacement pump 31 herein is connected in the hydraulic circuit in a novel manner facilitating and simplifying the control of the pumps to obtain the large quantity of fluid necessary to impart a rapid traverse movement to the head, the substantially smaller metered quantity of fluid necessary to impart a feed movement to the head, or to supply no fluid so as to bring the head to rest. 'Ihe manner in which the variable displacement pump is connected in the circuit also simplifies the circuit and permits all operating conditions to be obtained with continued operation of both the constant displacement pump 36 and the variable displacement pump 31 which is desirable because of the greater accuracy and more immediate response obtained in the movements of the head than can be obtained by starting and stopping of the pumps. To that end each cylinder 80 of the pump is connected between the conduits 60 and 6| to form part of the passage leading from the constant displacement pump 36 to the motor. Each cylinder is provided with a first or intake check valve |00 permitting flow of fluid from the constant displacement pump into the cylinder 80 but preventing return flow and with a second or exhaust check` valve I0| permitting flow from the cylinder 80 to the conduit 6I but likewise preventing return flow. Each of the check valves 'is yieldably urged to seated position by light springs |00 and I 0I', but the pressure at which the check valves open is not determined by the springs. The pressure at which intake valve |00 opens is determined by the force required to impart an intake stroke to the piston 8| and may,' y for example, approximate 50 pounds.

The pressure at which exhaust valve |0,| opens is determined by the pressure in conduit 6| and this pressure is maintained at apredetermined minimum but in excess of 50 pounds. This difference in the opening pressures of the check valves is essential in order that the variable displacement pump 31 may at times meter and limit the fluid supplied to the motor 35 and to effect a feed of the head I2.

Before describing the control means determining the rate at which fluid is supplied, to the motor 35, the means for maintaining a minimum pressure in the conduit 6I will rst be described.

It is highly desirable in machine tools, especially.

during feed movement of the tool or work carrying support, that a uniform rate 0f movement be maintained. For example, it is essential to prevent a jump of the support when the tool reaches the end of its cut and the resistance offered by the cut is suddenly removed, or when the tool strikes a defect in the workpiece, or when for any other reason the load on the motor driving the support issuddently varied 'and to prevent an overrunning of the Vsupport when the cut of the tool is such as to aid the motor. To that end meansis provided which is operative, upon a breaking through of the tool or when the cut of the tool isv such that it tends to advance the support, to control the discharge of fluid from A,

39 and is responsive solely to the pressure in the supply conduit 6 I.

The valve 39, shown diagrammatically inFigs.

4 to '7 and in section in Figs. 10 and 12, com- .prises a core |02 reciprocable in a bore |03 formed in the valve casing 45. One end of the bore is enlarged and is closed lby ya cap |04 threaded thereinto, while the smaller end is closed by a cap |05.l Formed in the casing and opening into the bore is an annular port |06 with which the discharge conduit 14 leading from the reversing valve 38 communicates. The valve core |02 is formedwith an annular groove |01 wider than the port |06 and normally disposed opposite the port. The land |08 formed by groove |01 at the end'of the valve core is adapted to engage a conical seat |09 formed in the bore to control discharge from the port |06, and the valve core |02 is normallyfurged by a spring IIO in a Adirection to seat the land |08 and prevent'discharge from'the port |06. Movement of the valve core |02 in a direction opposed by the spring |I0 permits discharge from the conduit 14 to the bore |03 and through a port III leading to the tank or reservoir 58. Such movement of the valve core s|02 is normally limited by engagement of the valve core with an annular ring I2 yieldably supported'in position by a compression spring I|3 abutting cap |04. v

Actuation of the lvalve 39 is dependent entirely upon the pressure of the fluid in the supply conduit 6| and to that end the upper end of the bore |03 is connectedwith the conduit 6I` through a. conduit |I5, annular port ||5' and a restricted passage I I5" in the valvecor-e |02 (see Figs.. 10 and V12). Thus only whenfthe pressure of the fluid in the'supply conduit 6| reaches a value determinediby ,adjustment of the spring II 0 is the valve vcorfel02 forced downwardly to -permit discharge ,from the' conduit 14 4and it is immaterial what proportion ofY the resistanpeto actuation of the motor 35, overcome by that pressure ofthe fluid in the supply conduit 6|, is

lmade up by the friction 'ofi'theihead I2 and by movement of the support. This resistance herein is preferably made Iarge and is utilized to prevent overrunning of the support at no load or under light cuts. Herein such'resistance may be,

for example, and preferably is, of a value such that it isv overcome by a pressure of, approximately one hundred pounds in the supply conduit to the motor.

With the support mounted so that the resistance to movement thereof ,under no load is overcome by a supply pressure of approximately one hundred pounds, spring |I0 is adjusted so the valve 39 permits unrestricted discharge fromv the motor under. normal conditions during a cut creating a positive Work resistance and during movement of the support under no load, but serves to restrict the discharge under abnormal conditions during such a positive cut, such as upon the breaking through of the tool, and during a cut creating a negative work resistance, such as a climb cut.

The operation of the valve may best be understood from the following examples: Assume iirst that the circuit is employed to actuate a support carrying a tool such as the drill I5 shown herein. As the tool is approached to the work, the resistance to movement of the slide at no loadv requires a pressure of one hundred pounds in the supply conduit and thus valve core |02 is forced downwardly against the action of the spring ||0 to permit unrestricted discharge through the conduit 14. As the tool engages the work, the pressure in conduit 6| rises so as to overcome the additional resistance caused by the cut of the tool and thus maintains Valve 39 open to its full extent. When the tool breaks through and the utes of the drill tend to advance the support and cause the same to jump forward, the pressure in conduit 6| immediately drops below one hundred pounds with the result that valve 39 closes and so restricts discharge of fluid from the motor that the support is prevented from jumping forward. For the second example,

pressure in conduit 6| of approximately onehundred pounds and thus opens valve 39 to permit unrestricted discharge ofziluid. However, upon engagement of the tool with the work the tool tends to advance the support more rapidly than the fluid which isrsupplied, to the motor. As a. result the pressure'inconduit 6| drops below one hundred poundsfandspring I |0fmoves valve core |02 in a"direction-.torestct vthe discharge of uid throughtliejconduit14, Such restriction of the discharge conduitcauses .a pressure to be built up in the dischargeside ofthe motor which resists and prevents overrunning of the support. This resistance varieswith, and is proportional to, the driving force acting on the support as a result of the reaction vof the tool and the work. The motor .isthereby retarded and the pressure in conduit 6| built up until it maintains valve 39 open to an extent that uid is discharged therethrough only at the rate metered by the pump 31.

It will be apparent from the foregoing that the valve 39 is normally wide open and permits unrestricted discharge through the conduit 14 during movement of the support at no load and during normal operation with a positive cut but that it immediately and instantly comes v-into play to restrict discharge and prevent a jumping forward or an overrlmning of the support when the tool breaks through or during a cut such that the reaction of the tool on the work tends 'to advance the support. As a result a unique circuit is provided in which during a cut creating a negative work resistance the pump means rate of movement of the support and of controlling the valve 39 in a manner to maintain a resistance to movement which prevents overrunning of the support and permitting a discharge of fluid equal only to quantity supplied by the pump means. It will also be apparent that the pressure which may be built up in the discharge side of the motor is entirely independent -of the strength of the spring H0. With this arrange-- ment, the power required to drive the pumps for feeding the work is reduced to a minimum as no power is dissipated in overcoming a back-pressure.

While the spring ||0 is here set at approximately 98 pounds to be overcome and thus malntain a pressure slightly in excess of 98, for example a pressure of approximately 100 pounds, this may be varied by adjustment of screw ||1 against which one end of spring ||0 abuts. The screw is locked in adjusted position by a cap screw I8 (see Fig.'10) It will be apparent that the pressure for which the valve 39 is adjusted is'also the minimum pressure at which the exhaust check valve I 0| opens, pressures above the minimum being determined by the load.

In addition to functioning to maintain a uniform movement of the head I2 under all conditions, the valve 39 also acts as a safety valve limiting the maximum working pressure in the conduit 6|. To that end the valve core |02 has an annular groove |20 communicating with an axial passage |2| discharging to the enlarged portion of the bore |03 with which communicates a conduit |22 leading to the reservoir. 58. Under norlmal conditions of operation movement of the valve core '|02 is not sufcient to cause groove v|2|.'| to register with port |I5 but, should the operating pressure in conduit 6| become excessive,

,the valve core |02 will be forced downwardly against the opposition of the spring I I3 until groove |20 registers with port I I5. This permits unrestricted discharge fromthe supply conduit 6| through the' valve 39 to the reservoir 58. The restricted passagel ||5 (see Figs. 10 and 12) communicates with the port v| I5 throughout the limit of movement permitted by the ring I2 and the-restriction proper is provided by a drilled set screw"v |23 threaded into the passage. -The restricted passage ||5 also serves to dampen the movement of the `valve core |02 and the usel of the set screw |23 makes possible va ready change of 'the restriction so that the valve may be adjusted to be immediately .responsive yet not oscillate.

' The meansl provided for controlling the supply of operating uid to the motor 35 from the piunps 36 and 31, so as to obtain the desired movements valve -40 having a iirst adjustment at which a large quantity of fluid is supplied to the motor to rapid traverse the head, a second adjustment at which a smaller quantity of uid is supplied to the motor at an accurately metered rate to obtain a feed movement of the head, and a third adjustment at which no iiuid is supplied to the motor so that the head is at rest. This is-all accomplished with continued operation of both the constant displacement pump 3S and the variable displacement pump 31.

The bypass valve 40 (see Figs. 4 and 10) comprises -a cylindrical bore |30 in the valve casing 45 within which is disposed a cylindrical member |3| the intermediate portion of which is in fluid-tight relation to the bore |30 and the ends of which are of smaller diameter than the bore and form narrow annular valve seats |32 and |33. Slidable in one end of the bore |30 is a valve, disk |34 .urged to seat on the valve seatr |32 by a light compression spring |35 abutting a cap |30 closing the bore. Slidable in the other 'end of the bore is a similar valve disk 36 urged to seat on the valve seat |33 by a heavy compression spring |31. The valve casing has an inlet port |38 opening into the bore between the intermediate portion of the member |3| and the valve disk |34 when seated and a similar port |39 opening between the intermediate -portion |3| and the valve disk |36 when seated. These ports are connected by branch passages to a conduit 40 communicating with the conduit 60 at a point intermediate the constant displacement pump 36 and the variable displacement pump. Leading from the interior of the member |3| are a pluralityof radial apertures |3I (see Fig. 10) opening' to an annular groove 3|" formed in the intermediate portion of the' member |3I. The groove |3| registers with yan annulargroove |30, in the bore |30, which has'a discharge port |4| leading to the reservoir 58. While the diagrammatic views (Figs. 4 to 8) would indicate separate return conduits from the valve 39 and the valve 40 to the reservointhe valv'es actually discharge to a common passage |4|' (see Fig-10).

and have a common return duct (not shown).

Spring |35 is capable of maintaining the disk |34 seated against low pressures in the conduit |40, for example, up to 5 pounds. Spring |31 is capable of maintaining disk |36 seated against y a substantially higher pressurey comparable with.

that required to open intake valve |00, namely '50 pounds, and this pressure furthermore may be yvaried by turning an adjusting screw |42 threaded into the valve casing. At the end projecting into the bore |30 the screw |42 carries a plate |43 against which the one end of the spring |31 abuts. The screw |42`is concealed by a plug |44. The valve disks are also adapted to be positively held seated'so as to prevent all discharge v of fluid through the port 4|. To that end each valve disk is pierced by a small aperture |45 Which perm/its leakage of fluid fromthe'fconduit |40 to the chambers formed behind the valve disks. Leading from the chamber formed behind the disk |34 is "a conduit 48 and leading from the chamber formed behind the valve disk |36 is a conduit |48. These conduits m-ay be closed, as Will later bezdescribed, to prevent discharge of fluid from the chambers. Because, as is apparent from an inspection of the drawings, the area of the valve disks exposed to the pressure of the fluid in the conduit |40 when the disks are seated is substantially smaller than the area of the disks exposed to the uid in the chambers formed behind the` disks, either orboth of the valve disks may be positively held seated by fluid pressure in the chambers by closing the conduits |48 or |49 or both.

When valve disks |34 and |36 are held positively seated by closing conduits |48 and |49, none of the fluid discharged by the constantdisplacement piunp 36 is permitted to return to the reservoir 58 throughthe bypass valve 40. As a result, the pressure in the conduit 60 builds up until it is capable of opening both intake valve |00 and exhaust valve |0| of the variable displacement pump 31. All of the fluid displaced by. the pump 36 is thus forced through the pist0n pump 31 to the conduit 6| and thence to' motor 35 to impart a rapid traverse movement thereto. pump 36 is now operating at a pressure in excess of that maintained in the supply conduit Because the constant displacement 6| by the valve 39, the fluid displaced by the pump `36 flows through the variable displace- 'ment pump 31 'without being metered even though the variable displacement pump continues to operate, the cylinder of the pump merely providing a passage for the flow of the uid. I

When conduit |49 is open but conduit |48 is closed, the bypass valve 40 maintains in the conduits 60 and |40 the pressure for which spring |31 is adjusted, for example 50 pounds.' Such a pressure .in the conduit 60 is capable of opening motor 35, and thus determinesthe feed movement of the head 2. The excess of fluid supplied by the constant displacement pump 36 over that meteredfby the Ivariable displacement pump 3'!v builds up' the pressure in 4conduit |40 s lightlyin' excess of the 50 .pounds for which 'the spring |31 is adjusted, and thereby unseats valve diskf|36and is returned through port |4| to the reservoir 58. Y

If conduit |48 is open the press'ure in conduit |40 is determined by spring |35 which,fas previously stated, maintains a pressure `of approximately 5 pounds. Under this condition the fluid in conduit ,60 is incapable of opening intake check valve |00 and all of the fluid supplied by the constant displacement pump flows through port |38 and thence through port |4| to be returned to the reservoir 58. Thus, though the constant/displacement pump as well as the variable displacement pump continue to operate, no fluid is discharged to the motor 35 and consequently no movement is'imparted to the head I2.

Pilot valve means 4| is provided for controlfling and coordinating reversing valve 38 and bypass'valve 40 so as to obtain the desired rate and direction of movement of the head I2. Herein the pilot valve comprises a cylindrical valve core slidable longitudinally in'a bore |56 -in the valve casing 45. Opening into the bore |56 is a port |51 and leading therefrom is a conduit |58 communicating with one end of the bore 62 of reversing valve 38. A port |59 also opening into bore |56 has a conduit |60 leading therefrom which communicates with the opposite end of the bore 62 of the reversing valve 38. Disposed diametrically opposite port |51 is a port |6| leading to the reservoir 58, and diametrically opposite-port |59 is a port |62 also leading to the reservoir 58. In close proximity to the ports |59 and |62 is an annular port |63 which is connected by conduits |64 and |65 to the conduit |40 leading to the bypass valve 40. An annular port |66 communicates With the conduit |48 leading to the /chamber behind valve disk 34 and an annular port |61 has leading therefrom a conduit |68 communicating at the other end with an annular port |69 -in reversing valve 38 and an adjacent annular port |10 in the reversing valve communicates with conduit 49 leading to the chamber formed behind valve disk |36`. There are in additionan annular port |1| connected -by a conduit |12 to the supply conduit 6|, an annular port |13 into which conduit 96 opens, -an annular port |14 leading to the reservoir 58, and an annular groove |15.

` The valve core |55`(vFig. 4) has formed therein 75 ployed. Dog 20| engages the pin the pilot valve from rapid approach to fast vslow feed to rapid return.

an axial passage |80, at one,end opening through the core to the bore |56 and at the other end: terminating in an oblique passage |8| communicating with a narrow annular groove |82 and a wide annular' groove |83 axially spaced. Adjacent the annular groove |83 is a second Wide annular groove |84 not in communication with the passage |80. Next is a narrow annular groove |85 which is in communication with the passage |80 through a port |80', then aradial duct |86, an annular groove |81, not in communication with the passage |80, and a wide segmental groove |88. i

For the cycle of operation to be imparted to the head 2, the valve 4| has ve positions, as indicated in Fig. 4, namely, stop, approach, fast feed, slow feed and return. The various positions of the valve are indicated and then valve yieldablyretainedin those positions (see Fig. l0) by a spring pressed ball detent gaging in \not`ches |9| formed in the surface of the valve core. The valve may be shifted manually to its various positions by means of a lever |92 pivoted on a shaft |93 and engaging one end of a pin |94 fixed in the valve core |55 oand projecting through longitudinal slots |95 in a tubular projection |96 of the valve casing. Automatic shifting of the valve is also provided for by the provision of dogs (see Figs. 1 to 3) suitably positioned on the. bar 43 to engage the lower projecting end |94.' of the pin |94. y Four dogs 200, 20|, 202 and 203 are here em- |94 to shift feed. Dog 202 shifts the valve from fast-feed to slow feed, and dog 203 shifts the valve from Dog200 shifts the valve from rapid return to stop. The dogs of course are shiftable along the bar 43 so as to vary the point in the movement of the \head lf2 when the change inthe rate of movement or the direction of movement takes place. It is believed obvious that the dogs might also be interchanged or more dogs employed to obtain a cycle different from the one here described.

The pilot valve 4| Bmay be shifted to approach position by direct manual actuation through the lever |92 or by means of the remote control valve 42. When the pilot valve is shifted by means of lever |92 the reversing valve 38 must also be` shifted manually fromfits `return position shown in Fig. 4 to its advance position shown in Fig. 5. To that end there projects through the left end cap 62' of the reversing valve a plunger pin 206 normally held outwardly (Fig. 10) by a compression spring 2,01 bearing at one end against the`v cap and at the other end I2|0 is vprovided with an axial passage 2|1 which against a knob 208 fixed on the outer endof the pin. l 4Pushing valve from the head returnposition shown in Figs. 4 and 10 Ato thehead advance position shown in Figs. 5 and 6. i A

Remote control valve 42 comprises a valve core Y 2 I0 slidable in a bore 2 which has an annular port 2|2 communicating by a conduit 2|3 with the bore- |56 of the pilot-,valveand an annular port 2 |4 communicating by.conduit 2|5 with the conduit |65. ALeading from the 4right end of the bore, as viewed in Fig. 4, is a Yconduit 2|6 whichdischarges to the reservoir 58. The valve core communicateswith the end of the bore 2| communicating with the conduit 2|6`and at. its inner lend communicates with an annular groove 2|8. .The core has in addition a wide annular Fig. 4 by a compressionspring 220 rapid I,

the pin 206 inwardly shifts the groove 2|9. 'I'he remote control valve is urged to and normally assumes the position shown in and may be shifted axially away from that position by any suitable means. Herein an electromagnet 22| is employed for that purpose.

When the remote control valve is in its normal position, shown in Fig. 4, it constitutes a return passage for the fluid discharged to the bore |56 of the pilot valve in certain positions thereof as will become apparent hereinafter. When the pilot valve 4| is in.stop position, a shift of the core 2 I0 of the remote control valve connects ports 2|4 and 2|2 to permit fluid from the conduit |40v to shift the pilot valve to rapid f approach position and to shift the reversing valve from return position vshown in Fig. 4 to advance position shown in Fig. 5. With the pilot valve in either the fast feed or slow feed position, a corresponding shift of the remote control valve to connect ports 2 I4 and 2 |2 shifts the pilot valve to rapid return position and returns' reversing valve from its 'advance position shown in Fig. 5 to its return position shown in Figs. 4 and '1. I

Having described the construction of the motor, the pumps and the valves, arfd having described the conduits or passages connecting the same, the -operation'and the course of the iiuid through the hydraulic circuit may best be understood from the followingdescription of the operation. Assume that the valves are in the positions shown in Fig.

I4, particularly with thepilot' valve 4| in stop position, but with motor I6 running to drive the drill, constant displacement pump 36 and variable displacementpump 31. Port |66, to which con- 2|3, port 2|2, groove 2|8, and axial passage 2|1 ,of the remote control valve, and conduit 2|6 to the reservoir 58. Thusthebypass valve 40 maintains in the conduits |40 and 60 only a pressure determined by spring |35 which is approximately 5 pounds. This pressure is insuiicient to open intake check valve |00. All of the fluid displaced by pump 36 is now bypassed by the bypass valve 40 and returned to the reservoir 58 through conduit 4| and no iiuid is supplied to the motor 35 so that the head |2 is at rest.

To take care of any leakage past check valve |0| and any slight displacement of pump 31, there isa slight opening between port |1| (see Fig. 4) and groove |83 permitting return of the oil to 'the reservoir through conduit 2|3 land remote control valve 42.

To impart a rapid approach movement to the head I2 the pilot valve 4| is shifted one step to the left to the position shown in Fig. 5. 'I'his may be done manually through the lever |92 in which case the reversing valve 38 also is shifted manuallyby pressing the plunger pin 206 inwardly. Preferably, however, the pilot valve and the reversing valve are shifted hydraulically under the control of the remote control valve 42. By shifting the core 2|0 of the remote control valve to ther left from its normal `position shown in Fig. 4, groove 2|9 bridges ports 2|4 and .2|2 so that pressure 2|3 to the bore bore |56 the uid ows through duct |86 and port through passage. |80 l51'and then through Fia conduit |58 to the left end of the bore 62 of the reversing valve 38 and shifts the same to the right to its-advance position shown in Fig. 5, pressure iluid behind valve 63 being relieved through conduit |60, port |59, groove |81, and lconduit |62. After having shifted the reversing valve 38 the fluid then acts upon core |55 Of/the pilot valve and shifts the same one step to the left tothe position shown in Fig. 5. The fluid is prevented from shifting the pilot valve more than one step because in its approach position (see 5) the vaxial passage |80 through groove |85 communicates with pori; |14 which leads to the reservoir 58. Though conduit 96 is in communication with the passage |80v the low pressure iluid is incapable of shifting piston 81. A fter shift of the reversing valve 3|!A and the pilot valve, the remote control valve is returned to normal position Vby spring 220 when-electromagnet 22| is deenergized.

This shift of the pilot valve to approach position closes port |66 and by preventing escape of fluid from the chamber behind valve disk |34 causes the valve disk to be positively seated by the pressure of the fluid flowing through the aperture |45 in the disk and trapped in the chamber behind the disk. Disk |36 likewise is#l` held positively seated by the pressure of the fluid in the chamber behind the disk because port. |61 also is closed and thus prevents discharge of lluid through conduit duit |68. With all return of fluid to the reservoir 58 prevented, constant displacement pump 36 builds up a pressure in the conduit 60 which is suiiicient to openexhaust check valve as `well as intake check valve |00 and all the uid displaced by the constant displacement pump 36 iilows through the variable displacement pump 31 to the supply conduit 6|. From the conduit 6| the iluid passes through ports 66 and 61 in the reversing valve 38, now bridged by a groove 15, and then through conduit 1| to the right y Vend of cylinder 55iof the hydraulic motor.

The uid in the right end of cylinder 55 tends l to move the same relative to the piston 56 and to force the iluid in the left end of the cylinder through conduit 10, ports 65 and 64 in the reversing valve, and conduits,v 12 and 14. Such discharge of fluid from/ the left end of cylinder 55 is, however, controlled by valve 39 the core of which is urged upwardly by spring |0 to engage valve seat |09 and thus prevent discharge from the conduit 14. 'I'he valve .39 is controlled solely by the pressure of the fluid in conduit 6| which is conducted to the bore |03 of valve39 through a conduit ||5. The pressure at which spring I0 is overcome may be varied by adjustment of screw H1, but with a pressure of 5 pounds maintained by the spring |35 and of 50 pounds maintained by thesprlng |37 of the bypass valve the pressure at which the spring l0 is overcome to permit ilow from the conduit 14 may be considered, for example, to be approximately 100 pounds. The pressure of the fluid in conduit 6| necessary to overcome the resistance to'movement of the slide at no load approximates 100 pounds and thus is sufcient to overcome municates with groove y pressure determined |49, reversing valve 38 and, conthe lower projecting end |94' of pin |94 and shifts the pilot valve another step to the left of its fast feed position, shown in Fig. 6. With the pilot valve in this position, port |66 is still closed so that the valve disk |34 is positively retained' seated. Port |61, however, now com' |83 in core |55 of the pilot valve and thence through passages |8| and |80, conduit 2| 3, port 2|2 and axial passage 2| 1 in the remote control valve, through conduit 2 |6 to the reservoir. 'I'hus fluid in the chamber behind valve disk |36 is free to escape through conduit |49, ports and |69 of reversing valve 38 now bridged by groove and conduit |68 to port |61 so that the valve disk is maintained seated only by the spring |31 which yields to permit bypass of fluid when the pressure in the conduit |40exceeds 50 pounds.

With the pressure in theconduits |40 and 60 limited to 50 pounds, the fluid in the conduit 6 0 is capable of opening intake check valve |00 and of imparting a return or intake stroke to the piston 8|, but is incapable of opening exhaust check valve |0| because there is at least the 100 pounds by the valve 39 that must be overcome. However, the fluid which is forced into the cylinder 80 by the action of the constant displacement pump 36 and trapped therein by the check valve |00 is forced from the cylinder by the piston 8| through the exhaust check valve 0| and into the supply conduit 6| leading to the motor 35. From the conduit 6| the fluid passes through the reversing valve 38 and to the hydraulicl motor 35,` as previously described. Only y,the fluid displaced by the pump 31 is now supplied to the motor 35 and the quantity supplied is accurately metered and determined by the displacement of the pump 31. 'I'he rate of movement of the head |2 is thus determined by the displacement for which the variable displacement pump 31 is adjusted.

The friction of the head plus the load created by engagement of the tool with the work in a positive cut results in a total resistance requiring a pressure in excess of 100 pounds in the conduit 6| to overcome the same. Thus valve -core |02 is maintained in open position as determined by engagement with annular ring ||2. "In this position there is unrestricted flow through the valve 39 so that no resistance is imparted by the valve 39 to movement of the motor 35 and head |2. However, should the tool bieak through,

or should the tool be taking a cut which tends, to advance the head, the pressure in conduit 6| would drop below 100 pounds, as described above, and spring 0 would immediatelyJ shift valve 39 to compensate for such variation by restricting ilow from the conduit 14 and thus provide the resistance necessary to ,prevent a jump or an overrunning of the head. Thus the valve 39 serves in a unique manner to prevent jump of thehead upon a lessening of the load such as a breaking through overrunning of the tive cut.

The valve 39 also acts as a relief valve. Should the head strike an obstruction or should the cut of the tool be too deep so that the working pressure in the conduit 6| becomes excessive, the core |02 of the' back-pressure valve Would be forced downwardly in vopposition to the spring ||3 until groove |20 registers with port ||5. Fluid from the conduit 6| would then Idischarge through Yconduit 5, port H5', groove 20 and of the tool, and preventsI head as a result of a negaplacement of the pump 31.

metering the fluid. Port |13 of the pilot valve,

however, with which conduit 96 communicates is `now connecteduthrough groove |84 with port |1| which is supplied through conduit |12 with high pressure iiuid from supply conduit. 6|. 'I'he other end 0f conduit 96 discharges to cylinder 88 of pump 31 and the pressure fluid thus supplied shifts the piston 81 from the position shown in Fig. 6 to the left an extent permitted by the spacing of the rings 90 and 9|. By such movement of the piston 81, the end of the arm 84 of the wobble plate 82 is forced into the oblique socket 85 of the shaft 49, thereby reducing the throw of the wobble plate 82 and correspondingf ly reducing the stroke of piston 8| and the dis- V A smaller quantity of metered fluid is now supplied by the pump 31 to the motor 35 and the head |2 has a correspondingly lower rate of movement.

Continued movement of the head I2 in a forward direction brings pin |94 into contact with the reversing dog 203 which shifts the pilot valve 4| another step to the left toU its return position shown in Fig. 7. Ports |59 and |63 of pilot valve 4| are now bridged by the segmental groove |88 and iiuid flows from conduit |40 through conduit |65, conduit |64, ports |63 and |59, and conduit |60 to the right end of *boreA 62 of the reversing valve 38, thereby forcing the valve coreu 63 to the left from the position shown in Fig. 6 to the position shown in Fig. '1, the pressure fluid at the other end of valve 63 being relieved through vIGI.

charged through conduit 1|-,l ports 61 and 68,

conduit 13 and conduit 14 through the backpressure valve 39 as previously described. The shift df the reversing valve also closes port |69 thereby causing pressure to build up in the chamber behind valve disk |36, positively closing the same. Port |68 is still closed by the pilot valve thereby maintaining disk |34 positively seated so 'that the exhaust valve 40 now again prevents any return of fluid to the reservoir 58 and all of the iiuid discharged by the constant displacement pump 36 is forced through the variable displacement pump 31 without being metered so as to impart a rapid traverse return movement to the head l2.

Should it be desirable to retard or delay the reversal of the head I2 so as to obtain a dwell, this may be accomplished by adjusting the dog 203 so as to effect only a partial Shift of the pilot valve 4|. Depending upon the extent of the partial shift of the pilot valve, a greater or lesser opening is obtained between the port |59 land the groove |80, thus determining the rate at which fluid is supplied to the right end of the reversing valve 38 and thereby determining the time required to shift the valve from its advance to its return position. As the valve is shifted it gradually closes ports and 61, brings head |2 to a gradual stop, retains both ports closed for a short dwell and then gradually opens them to reverse the head I2. Preferably a positive stop dog (not shown) is employed under such conditions to assure complete reversal. The time of dwell for a given shift of the pilot valve is always the same and independent of the pressure required to actuate the slide because the iiuid effecting the reversal is taken from the conduit |40 and not conduit 6|.

The head |72 may also be reversed prior to engagement of the pin |94 with the reversing dog 203 at any time during the fast feed or slow feed thereof by manually shifting the pilot valve 4| or by actuating the remote control valve 42. With the pilot valve in either fast feed position, shown in Fig. 6, or slow feed position, shown in Fig. 8, a shift of the remote control valve to the left connects ports 2|2 and 2|4. Pressure fluid would then iiow from the conduit |40 through conduit |65, conturns the pilot valve to stop position. In that position, as previously described, the chamber behind valve disk |34 is connected to the reservoir through the pilot valve so that the bypass valve maintains -only a pressure of approximately 5 pounds in the conduits 60 and |40 which is insuicient to open intake check valve |00. Thus,

though the pumps 36 and 31 continue to oper-J ate, no fluid is supplied to the motor 35.

While the diagrammatic views (Figs. 4 to 7) show the positive displacement piston pump 31 as having but a single cylinder and piston, it is to be remembered that the pump has in fact a plurality of cylinders and pistons with each vcylinder connected in the manner here shown,

as more particularly disclosed in my copending applications Serial No. 60,646, led January 24, 1936, now abandoned, and Serial No. 141,327, filed May 7, 1937. f

The term unmetered, employed throughout the specificationl and claims in describing the fluid supplied by the rotary pump 36, is not intended to mean that the discharge from pump 38 is irregular and indeterminate. employed merely to characterize and distinguish the'slightly variable and, in this instance, large output of a rotary pump from the minutely measured and, in this instance, small output of a positive displacement piston pump. The terms metered and unmetered are primarily a matter of degree. Furthermore they are employed in the sense that during feed of the support the piston pump 31 measures or meters the quantity of fluid supplied whiley during rapid traverse uid flows through the piston pump -in quantities independent of the displacement The term is movement in either direction when "the pllt valve is inl 'stop position. Neither tlhe check lvalve lill nor 'the valve 39 yield to pressure built up within the motor by the application of exspeed of movement of the member, having a first,

adjustment rendering said rst means effective to supply fluid to said motor to drive the member at a high speed, a second adjustment rendering said second means effective to supply fluid to drive the member at a lower speed, and a third adjustment rendering both said ilrst and said second means ineiective to supply fluid to said motor whereby the member is at rest. C

2. A hydraulic circuit comprising a hydraulic motor for imparting movement to a member at diierent speeds, a first pump for supplying a large quantity of iluid to said motor at a high rate to impart a high speed to the member, a second piston '(pump for supplying a smallelr metered quantity of fluid to said motor at a lower rate to impart a lower speed to the member and interposed between said first pump and said motor, a control means adjustableto be variably responsive to iluid pressure determining which of the iluid supplying means is effective to supply iluid to said motor to govern the speed of movement of the member, and means effecting the adjustments of said control means.

3. In a hydraulic circuit a hydraulic motor, a variable pressure pump for supplying operating iluid to said motor, fluid metering and pressure boosting means interposed between said pump and said motor operable under predetermined pressure conditions to meter the quantity of fluid passing therethrough and operable under other pressure conditions to permit fre-e unmetered ilow therethrough,l and control means governing the pressure of the iluid supplied to said metering and boosting means by said variable pressure pump to obtain a metered or an unmetered supply of iluid to the motor.

4. A hydraulic circuit comprising a hydraulic motor forrdriving a member at different speeds,\a

large output pump for supplying operating fluid to said motor at a high rate to drive the member at a high speed, a passage leading from said pump to said motor, a first and a seco-nd check valve in the passage disposed to permit ilow in a direction from said pump to said motor but preventing ilow in the .opposite direction, means seating said second check valve to permit opening thereof only upon the creation of a predetermined pressure higher than that required to open the ilrst check valve, a positive displacement pump of smaller capacity than said large output pump communicating with the passage leading from the large output pump to said* motor intermediate the check valves and operable to supply a metered quantity of fluid to said motor at a lower rate to drive the member at a lower speed, and control means governing the rate at which iluid is supplied to said motor having a first adjustment in whichiluid isv supplied to the motor in accordance with the capacity of the'large output pump to drive the member at a high speed and" a second adjustment in which a metered quantity of fluid determined by the output of the positive displacement pump is supplied to said motor to drive the member at a lower speed.

5. A hydraulic circuit comprising a hydraulic motor for driving a member at different speeds, a variable pressure large output pump for supplying fluid to said motor at a high rate, a positive displacement piston pump for supplying fluid at a lower metered rate having each cylinder of the pump connected between the large output pump and the motor so that all fluid supplied to 'the motor flows through the piston pump, an intake check valve for each cylinder, an exhaustfcheck valve for each cylinder, both of said check valves being disposed to permit ilow only in a direction from said large output pump `to the motor, and control means determining which of said pumps is effective to supply iluid to said motor so as to obtain a large unmetered supply of iluid for driv- A ing the member at a high speed or a smaller metered supply of fluid for driving the member at a lower speed.

6. A hydraulic circuit comprising a hydraulic motor for driving a member at different speeds, a variable pressure large output pump for supplying fluid to the motor at a high rate to imparta high speed to the member, a positive displacement piston pump for supplying fluid at a lower metered rate having each cylinder of the pump connected between the large output pump and the motor so that all fluid supplied to the motor ilows through the piston pump, an intake check valve foreach cylinder permitting flow only into the cylinder and opening only at a predetermined pressure, an exhaust check valve for each cylinder permitting flow only out of the cylinder and opening only at a pressure higher than that required to open the intake check valve, and control means determining the rate at which iluid is supplied to said motor having a rst adjustment causing the discharge pressureof the large output pump to equal the pressure at which the exhaust check valve opens to obtain an unmetered ow to the motor of a large quantity of fluid through the piston pump to drive the member at a high speed, and a second adjustment causing the discharge pressure -of the large output pump to exceed only the pressure at which the intake valve'opens to obtain a metered ilowof fluid to the motor at a rate determined by the displacement of the piston pump, for driving the member at a lower speed.

7. A hydraulic circuit comprising a hydraulic "motor for driving a member at different speeds, a

cylinder permitting ilow of iluid only into the cylinder, an exhaust check valve for each cylinder permitting flow of fluid only out of the cylinder, means controlling the exhaust check valve to permit opening thereof only. at a pressure substantially higher than that required to open the intake check valve and impart an intake stroke to the piston in the cylinder, and a bypass valve connected between said large output pump and the intake check valve of each cylinder having a rst adjustment preventing any bypassing of fluid therethrough whereby all fluid discharged by the largev output pump flows unmetered through the piston pump to the motor to impartA a high speed vto the member, anda second adjustment maintaining a pressure of the fluid discharged by the large output pump capable of opening the intake check valve and of imparting an intake stroke to the piston, but incapable of opening the exhaust check valve whereby the piston pump supplies a metered quantity of fluid to said motor to drive the member at a lower rate, said bypass valve bypassing the excess -offluid supplied bythe large' output pump over that metered by thel piston pump.

8. A hydraulic circuit comprising a hydraulic motor for driving a member at different speeds, a continuously driven variable pressure pump of large output for supplying lluidto said motor at a high rate, a continuously driven positive displacement piston pump for supplying fluid at alower metered rate having each cylinder of the pump connected between the large output pump and the motor so that all fluid supplied to the motor flows through the piston pump, means for imparting' an exhaust stroke onlylto the piston in each cylinder, an intake check valve for each cylinder permitting flow of fluid only into the cylinder, an exhaust check valve for each cylinder permitting flow 'of iluid only out of the cylinder, means controlling the exhaust check valve to permit opening thereof only at a pressure substantially higher than that required to open the intake check valve and impart an intake stroke to the piston in the cylinder, andr a double bypass valve connected between the large output pump and each intake check valve for determining the rate at which fluid is supplied to said motor by controllingjthe discharge pressure of the large output pump having a iirst adjustment at which no fluid is bypassed thereby maintaining a discharge pressure of the large output pump capable of opening both check valves to obtain an unmetered flow of fluid to said motor at a high rate, a second adjustment maintaining a discharge pressure capable of opening only the intake check valve to obtain a supply of fluid to said motor at a metered rate determined by the displacement of the piston pump, .said bypass valve bypassing the excess of fluid supplied by the large output pump over that metered by the piston pump, and

.a third adjustment maintaining a discharge presof open- A sure of the large output'pump incapable ing the intake check valve whereby all fluid is bypassed and no fluid is supplied to said'motor.

9. In a hydraulic circuit for reciprocating a member, a hydraulic motor, a reversing valve directing the flow of fluid to and from said motor,

a pump through which passes all of the fluid supplied to said hydraulic motor, said pump being operable under predetermined conditions to meter the quantity of fluid supplied to the hydraulic motor and to boost the pressure of the fluid, and operable under other conditions to provide a passage for the unmetered llow of fluid, and means including a source of uid under pressure conl trollable to render the pump capable or incapable of metering the quantity of uid'passing therethrough.

10. A hydraulic circuit comprising a reversible hydraulic moto-r for imparting movement to a member at different speeds and in opposite directions, a first pump for supplying a large quantity of llud to said motor at a high rate to impart a chine tool through a i ineffective to supply fluid to said motor to obtain dilierent speeds of the member, and a pilot valve governing and coordinating said bypass valve and said reversing valve` to obtain a predetermined cycle of operation of the member.

. 11". A hydraulic circuit comprising a reversible hydraulic motor for driving a support of a mapredetermined cycle, a iirst supplying a large quantity of fluid to said motor at a high rate to impart a high speed to the member, a second pump for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a lower speed to the member, means for driving saidpumps continuously, a reversing valve for directing the fluid supplied to said motor having an advance and a return position, an adjustable bypass valve having a first adjustment rendering said first pump effective to supply fluid to said motor, a second adjustment rendering said second pump eiective, and a third adjustment rendering both pumps ineffective to supply fluid, and a pilot valve pump for controlling said bypass valve and said reversing high rate to impart ahigh speed to the member,-

a supply passage leading from the pump to the motor, a first and a second check valve in the passage disposed to permit flow only from the pump to the motor, a second pump for supplying a smaller metered quantityof fluid to said motor at a lower rate to impart a lower speed to the member, said second pump communicating with the passage intermediate the check valves, a. re-

' versing valve for directingithe fluid supplied to said motor to effect reversal thereof, means operable to control the dlscharge'of iiuid from said motor maintaining a predetermined minimum pressure in the supply passage against which said second check valve opens, a bypass valve connected to the passage intermediate the lirst pump and the lirst check valve having selectively different adjustments maintaining the discharge pressure of the first pump above or below the pressure against which said second check valve opens, and a pilot valve coordinating the adjustments of the bypass valve and the position of the reversing valve. A

13. A hydraulic circuit comprising a reversible hydraulic motor for driving a member at differhaving selectively different adjustments to determine the rate at which fluid is supplied to said motor, a pilot valve for coordinating and controlling' the adjustment and position of said control means and reversing valve toobtain a demeans to eiiect reversal of said motor, means controlling the discharge from said motor to maintain a minimum pressure in the supply side of the motor under varying load of the member, control means governing the rate at which fluid is supplied to said motor to obtain the diierent speeds of the member, means coordinating said control means and said reversing means to obtain a predetermined cycle of operation of the member, a remote control for actuating said coordinating means to initiate the cycle of operation, and dogs actuating said coordinating means automatically to change the rate and direction of movement of the member. y

l5. A hydraulic circuit comprising a reversible hydraulic motor for driving a member through a predetermined cycle of'movement at diierent speeds, a rapid traverse pump for supplying a quantity of iiuid to said motor at a high rate to impart a high speed to the member, a feed pump for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a comparatively lower speed to the member, a reversing valve for directing the fluid supplied by said pumps to effect reversal of said motor, means controlling Vthe discharge of iiuid'from said motor responsive to the pressure of the iiuid supplied to the motor, control means governing the rate at which uid is supplied to said motor by said pumps to obtain the different speeds of the member, a pilot valve coordinating said control means and said reversing valve to obtain the predetermined cyole of movement of the member, a remote control `valve for actuating said pilot valve to initiate the cycle of movement, and dogs actuating said pilot valve automatically to change the speed and the direction of movement of the member'at predetermied points in the cycle.

16. A hydraulic circuit comprising a reversible hydraulic motor for driving a member through a predetermined cycle of movement at different Speeds, a variable pressure pump for supplying a large quantity of fluid to ,said motor at a high rate to impart a high speed to the member, a positive displacement pump for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a comparatively low g speed to the member,` a reversing valve directing theiiuid supplied by said pumps to effect reversal of said motor, means responsive to the pressure of the fluid discharged by said variable pressure pump yielding when the pressure reaches a predetermined value to permit'unmetered flow of the fluid dischargedby the variable pressure pump to said motor, means controlling the discharge of fluid fro'm said motor to maintain a minimum pressure at which said first mentioned means yields, a by-pass valve controlling the pressure of the 4iiuid supplied by said variable pressure pump to govern the rate at which uid is supplied to said motor to obtain the diierent speeds of the member, said by-pass valve having a first adjustment maintaining a pressure capable of actuating said pressure responsive means to cause all the fluid discharged by the variable pressure pump to be supplied to said motor, and a second adjustment maintaining a pressure incapable of actuating the pressure responsive means so that only the iiuid metered by said positive displacement pump is supplied to said motor, a pilot valve for coordinating the adjustments of said bypass valve and the positions of said reversing valve to obtain the predetermined cycle of movement, a remote control valve for actuating said pilot valve to initiate the cycle of movement, and dogs for successively actuating said pilot valve to effect a change in the speed or direction of movement of the member or both at predetermined points in the movement thereof.

17. A hydraulic circuit comprising a reversible hydraulic motor for driving a member through a predetermined cycle of movem'ent at different pump for supplying iiuid to said motor at a high rate to impart a supplying a metered quantity of iluid tosaid motor at a low rate to impart a lower speed to the member, said pumps being connected in series so that all of the iluid supplied to said motor passes through the piston pump, a reversing valve for directing the fluid supplied by said pumps to effect reversal of said motors, a first check valve in the passage from the variable pressure pump only in a direction from said pump to said motor and opening at a predetermined pressure, a second check valve in the passage from the variable pressure pump to said motor, also permitting ow only in a direction from the pump to the motor and opening only at a pressure higher than said first check fluid is by-passed and allfluid discharged by said varible pressure pump passes without being metered through the piston pump to said motor, a second adjustment maintaining a pressure capable of opening only said first check valve whereby a metered quantity of fluid `is supplied to said miotor by said piston pump, and a third adjustment maintaining a pressure incapable of opening either of said check valves whereby no fluid is supplied to said motor, a pilot valve for coordinating the valve and the position of said reversing valve to obtain a predetermined cycle of movement of the member, a. remote control valve actuating said pilot valve to initiate the cycle of operation, and a plurality of dogs actuating said pilot valve to change the adjustmentof said by-pass valve and the positionof said reversing valve to obtain the predetermined cycle of movement of the meinl ber.

and a positive displacement pump,

adjustments of said by-pass A pass valve connected in circuit with the pumps and controlling the rate at which uid is supplied to the motor comprising a casing having a bore therein, two`annular valve seats in the bore spaced from. the walls of the casing, a supply conduit discharging to the bore and a port leading from the bore, two valve disks slidable in the bore and adapted to engage the respective seats to control the ow of uid through the valve, a iirstspring urging one of the valves to seated position yieldable at a low pressure, a second spring urging the other of the disks to seated position yieldable at a higher pressure, and means for maintaining said disks positively seated to prevent the bypassing of any ud.

19. In a hydraulic circuit for driving a member at diierent speeds, a variable pressure pumpfor supplying operating fluid, a bypass valve controlling the discharge pressure of the pump comprising a bore in the valve casing, a tubular member in the bore with its ends spaced radially from the walls thereof to form annular valve seats, a supply port communicating with the bore intermediate the endskof the member, a discharge port communicating with the interior of the member, a first valve disk slidable inone end of the bore, a light spring urging the disk to seated position, a second valve disk slidable in the other end of the bore, a heavy spring urging the disk to seated position to permit opening thereof onlyat a substantially higher pressure, a small aperturein each disk leading from the supply port to the chambers formed behind the disks, ducts leading from the chambers behind the disks, and valve means controlling said ducts to cause either or bothof said disks to be positively held seated by fluid in the chambers behind the disks.

20. In a hydraulic circuit, a hydraulic motor, means supplying operating iluid to said motor including means operative under all conditions to prevent return flow through said uid supply means, means controllingr the ow of all exhaust fluid from said motor, and means responsive nary magnitude.

2l. In a hydraulic circuit, a hydraulic motor, means supplying operating fluid to said motor, a connection Abetween said motor and said fluid supplying means including al check valve preventing return ilow through said connection, said connection being the only line leading to the motor, a passage through which flows the exhaust uid from said motor, a valve solely controlling the ow of exhaust fluid spring pressed to closed position, said last named valve being incapable of openingl Linder the pressure of the exhaust fluid, and pressure responsive means operable to open said valve having communication with the' connection between said motor and said uid supplying means. Y. A

22. A hydraulic circuit comprising a reversible' hydraulic motor for imparting movement".` to a member at dilerent speeds and in opposite directions, a rst means for supplying a large quantity of fluid4 to said motor at a high rate to impart a high speed to the member, a second means for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a lower speed to the member, a reversing valve for directing the iiuid supplied to said motor to effect reversal thereof, control means determining Which of said lluid supplying means is eiective to supply fluid to said motor to obtain the dilerent speeds of the member, a pilot valve governing and coordinating said control means and said reversing valve to obtain apredetermined cycle of operation of the member, and a remote control valve operable to shift said pilot valve to a position for initiating movement of the member.

23. A'hydraulic circuit comprising a reversible hydraulic motor for driving a member at diierent speeds and in forward and return directions, means for supplying liuid to said motor at different rates to obtain a high speed ol the member or a lower speed of the member, a reversing valve directing the uid supplied to said motor to eiect reversal thereof, control means governing the rate at which fluid is supplied to said motor, a pilot valvel governing and coordinating said control means and said reversing valve having stop, high speed forwardflower speed forward and return positions, and a remote control valve Agoverning a supply of operating fluid for the pilot valve operable to shift the pilot valve from stop to high speed forward position and from lower speed forward to return position.

24. In a hydraulic circuit, a hydraulically shiftable reversing valve having an advance and a return position, a pilot valve having a stop,.rapid approach, feed and return position, and a remote control valve operable' with the pilot valve in stop position to control a supply of uid shifting the reversing valve to advance position and the'pilot valve to rapid approach position, and operable with the pilot valve in feed position to control a supply oi uid shifting the pilot valve to return position and the reversing valve to return position.

25. In a hydraulic circuit, a hydraulically shiftable reversing valve having an advance 'and a return position, a pilot valve comprising a casing having a bore and a core slidable therein, a iirst conduit leading from the bore in the pilot valve to one end of the reversing valve, a second conduit leading from the bore to the other end of the reversing valve, a first pressure fluid supply conduit opening to the bore, a return port leading fromthe bore, said port and conduits being controlled by the core, a second pressure uid supply conduit opening to the bore, and a valve in said second supply conduit, said pilot valve core having a rst position effectively connecting the bore to said rst conduit leading from the bore to the reversing valve and closing saidv return port and sald rst supply conduit, a second position connecting the bore to said return port and maintaining said first supply conduit closed, a third position closing said return port and maintaining said first supply conduit closed, and a fourth position connecting said rst supply conduit to said second conduit leading from the bore to said reversing valve.

26.. A hydraulic circuit comprising a yreversible hydraulic motor for driving a member in forward and return directions, a constant displacement pump for supplying fluid to thermotor at a high rate to impart a high speed to the member, a variable displacement pump for supplying uid to the motor at a lower rate to impart a lower speed to the member, said variable dis-y placement pump having a` cylinder and a piston movable therein to adjust the displacement of the pump, a reversing valve for directing the lluid supplied by said pumps to effect reversal of said motor, control means gfverning the rate at which fluid is supplied to said motor by said pumps to obtain the different speeds of the member, and a pilot valve coordinating said control means and said reversing valve to obtain a predetermined cycle of movement 'of the member, said pilot valve having a first position adjusting or positioning said control means and reversing valve to obtain a fast speed of the member, and a second position retaining said reversing valve and control m'eans in the same position or adjustment while connecting the supply of operating uid to .the cylinder of said variable displacement pump to actuate the piston in a direction causing a reduction in the displacement of the pump to obtain a slow feed of the member.

27. A hydraulic circuit comprising a/hydraulic motor for imparting movement to a member at different' speeds, a first pump for supplying fluid to said motor to drive said member at a low rate of movement, a second pump operable to supply uid to said motor to drive said member at a higher rate of movement, means responsive to the discharge pressure of said second pump controlling the period when said second pump is operative to supply fluid to the motor, and means governing the discharge pressure of said second pump.

28. A hydraulic circuit comprising a hydraulic motor for imparting movement to a member at different speeds, a variable pressure pump capable of supplying a large quantity of fluid to said motor at a high rate to impart a high speed to the member, a positive displacement pump for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a lower speed to the member, a fluid reservoir from which the operating fluid is drawn, and a valve connected in circuit intermediate the reservoir and at least one of the pumps operable to govern the rate at which fluid is supplied to said motor, said valve having a first adjustment at which no fluid ows therethrough rendering said variable pressure pump effective to supply fluid to the motor thereby driving the member at a high speed, and a second adjustment permitting flow therethrough at a predetermined pressure of fluid displaced by said variable pressure pump for rendering only said positive displacement pump effective to supply fluid at a metered rate to drive the member at a lower speed.

29. A hydraulic circuit comprising a hydraulic motor for imparting movement to a member at different speeds, a variable pressure pump capable of supplying a large quantity of fluid to said motor at a high rate to impart a high speed to the member, a positivel displacement pump for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a lower speed to the member, a reversing valve connected, in circuit intermediate said pumps and said m"` tor for directing the fluid to drive the motor in opposite directions,v said pumps discharging directly to said reversing valve, a by-pass fluid circuit, and a valve connected in said by-pass circuit operable to govern the rate at which fluid is supplied to said motor, said valve having a first adjustment in which the valve is closed preventing the :dow of uid therethrough for rendering said variable pressure pump effective to supply fluid to the motor thereby driving the member at a high speed, and a second adjustment permitting the ow therethrough at a predetermined pressure of uid displaced by said variable pressure pump for rendering only said positive displacement pump effective to supply uid at ka metered rate to drive the member at a lower speed.

t 30. A hydraulic circuit comprising a reversible hydraulic motor for driving a member at different speeds and in opposite directions, means for supplying fluid to said motor at a high vrate to impart a'high speed to the member or at a lower rate to impart a lower speed to the member, a reversing valve directing the fluid supply to the motor to effect reversal thereof, control means having selectively different adjustments to determine the rate at which fluid is supplied to said motor, a pilot valve for coordinating and controlling the adjustment and position of said control means and reversing valve to obtain a desired 'cycle of movement of 'the member, and a remote control valve operable to shift said pilot valve to initiate the cycle of operation.

31. A hydraulic circuit comprising a hydraulic motor for driving a member through a predetermined cycle of movementvat different speeds, a first means for supplying a large quantity of fluid to said motor at a high 1rate to impart a high speed to said member, a second means for supplying a smaller metered quantity of fluid to said motor at a lower rate to impart a comparatively low speed to the member, means for directing the fluid supplied by said first and sec- V,ond means to effect reversal of said motor, control means governing the rate at which fluid is supplied to said motor to obtain the different speeds of the member, means coordinating said control means and said reversing means to obtain a predetermined cycle of operation of the member, a remote control for actuating said coordinating means to initiate the cycle of opera- I tion, and dogs actuating said coordinating means automatically to change the rate and direction of movement of the member. i

32. A hydraulic circuit comprising a hydraulic motor for imparting movement to a member at different speeds, a first pump for supplying fluid to said motor at a low rate, a second pump operable to supply fluid to said motor at a higher rate, a common conduit through which fluid from said pumps is discharged to said motor, meansl responsive to the discharge pressure of said second pump -controlling the period when said second pump is operative to supply fluid to the motor, means governing the discharge pressure of said second pump, a conduit through which all the fluid is discharged from said motor,

and a valve operable to control the flow through said discharge conduit responsive only to the pressure of the fluid supplied to said motor.

33. In a hydraulic circuit, a hydraulic motor, a variable pressure pump for supplying operating fluid to said motor, a fluid'supply conduit leading 'i from said pump to said motor, fluid metering and pressure boosting means interposed in said conduit between said pump and said motor operable under predetermined pressure conditions to meter the quantity of fluid passing therethrough and operable under other pressure conditions to permit free unmetered flow therethrough, control means governing the pressure of the fluid supplied to said metering and boosting means by said variable pressure pump to obtain a metered or an unmetered supply of fluid to the motor, a conduit through which the fluid from said motor is discharged, and means in said discharge conduit operable to control the flow of fluid therethrough, said means being responsive to and 2,214,389 solely actuated by the pressure of the uid supplied to said motor.

34. A machine tool comprising, in combination, a bed, a tool support and a Work support relatively movably supported upon said bed, a hydraulic motor for driving one of said supports at feed and traverse rates, pump means operable to supply fluid to said motor at different rates to obtain feed or traverse movement, a single fluid supply conduit connecting said pump means With said motor, a single discharge conduit through which fluid is discharged from the motor both when driven at feed rate and when driven at rapid traverse rate, a valve disposed in said discharge conduit operable to control the loW of fluid therethrough, said valve being non-responsive to the pressure of the uid discharged, a spring normally urging said valve to closed position, and means responsive to the pressure of the fluid in the supply conduit for urging said valve to open position, said means and said spring being adjusted to cause the Valve to assume a Wide open position permitting unrestricted discharge when the pressure in the supply conduit equals that required to drive the motor at a rapid traverse rate under no load.

GUNNAR A. WA'HIMARK. 

